Cute attempt by Mr Forbes but overlooks the simple fact that water precipitates out of the atmosphere, giving it an obvious self-limiting mechanism and making it significantly different from CO2. His alternates are not exactly water-free either.
A “greenhouse gas” is one capable of absorbing infra-red (IR) radiation.
The most common atmospheric gases with such properties are water vapor and carbon dioxide (CO2). Water vapor is far more abundant with an average of 20,000 parts-per-million (ppm) in the atmosphere compared to just 395 ppm of CO2. Moreover water vapor is more effective as a greenhouse gas because it can absorb IR radiation over far more bands of the IR spectrum.
Therefore, if man-made CO2 causes dangerous global warming, (a dubious proposition anyway), then man-made water vapor is far more dangerous.
The two main electricity generation fuels in Australia are coal and gas. Coal is a dense fuel with a high carbon content which, when burnt, produces mainly CO2 with some water vapor. Natural gas has more hydrogen and less carbon and produces a higher proportion of water vapor, the main greenhouse gas.
Thus if the climate alarmists are really scared of man-made greenhouse gases, they should be promoting coal instead of gas or systems that need 100% gas backup, such as wind.
And if they believe a tax on man-made greenhouse gases will control the climate, a tax on steam makes more sense than a tax on carbon dioxide.
Finally, if they want “zero emissions” of either greenhouse gas, the only significant energy sources that qualify are nuclear, hydro and geothermal.
Maybe the climatists are not fair dinkum